Fix score() issue (#4194)

### What problem does this PR solve?

as title

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

Signed-off-by: jinhai <haijin.chn@gmail.com>

rag/utils/infinity_conn.py

     if df_list:
         return pl.concat(df_list)
     schema = dict()
-    for fieldnm in selectFields:
-        schema[fieldnm] = str
+    for field_name in selectFields:
+        if field_name == 'score()': # Workaround: fix schema is changed to score()
+            schema['SCORE'] = str
+        else:
+            schema[field_name] = str
     return pl.DataFrame(schema=schema)
 
 @singleton
         self.connPool.release_conn(inf_conn)
         res = concat_dataframes(df_list, selectFields)
         if matchExprs:
-            res = res.sort(pl.col("score()") + pl.col("pagerank_fea"), descending=True, maintain_order=True)
+            res = res.sort(pl.col("SCORE") + pl.col("pagerank_fea"), descending=True, maintain_order=True)
         res = res.limit(limit)
         logger.debug(f"INFINITY search final result: {str(res)}")
         return res, total_hits_count